1. Field of the Invention
The present invention relates to a method and apparatus for providing stereo television audio signals for recording on a recording medium or for transmission over a transmission channel in a stereophonic system or a multi-sound system.
2. Description of the Related Art
The communications technology for providing television signals is based on established infrastructure standards. These are very specific formats for transmitting signals to television receivers via radio frequency transmissions and via cable. In the United States, television signals must conform to the National Television Standards Committee (NTSC) standard. The NTSC calls for 525 lines of resolution transmitted at 60 half frames per second. The composite signal transmitted from a broadcast television facility includes the radio frequency (RF) carrier plus video signals containing color and luminosity information, audio signals containing sound information, and a Multichannel Television Sound (MTS) signal for deriving stereophonic audio separation. The composite signal minus the carrier is used for direct connection (i.e. wired connection) of video and audio signals.
Currently, there are only two ways of connecting a home entertainment video device such as a satellite receiver, a video cassette recorder (VCR), a laser disk player, etc. to a television receiver. The first method is a direct connection by shielded cable, of the baseband video, and of the left and right audio terminals between the two devices, using discrete cables for each signal. The second method, which is used extensively in the United States, is the use of signals from a RF modulator unit inside the source unit which combines video and audio information. The signals from the RF modulator provides the output signal on a single coaxial cable and emulates a standard broadcast channel to the television receiver. Although the use of the RF modulator signal eliminates the need for two additional discrete cables, it does not provide a high quality stereo audio output.
One approach to this problem is the implementation of a discrete analog stereo audio encoder that is installed external to the television receiver. Such a stereo audio encoder is complex and expensive, and thus precludes its use on low cost home entertainment products.
Accordingly, there is a need in the technology for a method and apparatus for generating stereo audio signals, including an MTS stereo composite signal, for transmission to a television receiver or a VCR, that is simple and can be easily implemented into low cost home entertainment products.